'Dangerousness' is not a term, however, that can be defined in the same
manner across jurisdictions and through time. In English speaking nations, when
dangerous offender laws were first passed in the early part of the twentieth
century, property offences were considered to be harmful acts. Thus, property
offenders were classified as dangerous and were incarcerated indeterminately
along with violent dangerous offenders (Pratt, 1996). In recent decades, the
concept of dangerousness has narrowed considerably to encompass an offender's
potential to commit acts of violence or those of a sexual nature. While it can
be said that dangerousness is the potential of an individual to cause future
harm to others, how a legislative body defines 'harm' is key to the definition
of dangerousness.

Historically, American dangerous offender legislation (at both the federal
and state levels) has focused primarily on sexual offenders. In the late 1930s,
Sexual Psychopath laws were introduced in many American states that were
formulated on the premise that dangerous sexual offenders were neither legally
insane nor normal. Thus, these offenders did not belong in mental institutions
but needed to be incarcerated for the purpose of public protection (Pratt,
1996). Early sex offender laws were based on a clinical model of assessing and
dealing with dangerous offenders. According to this model, those who commit
serious violent or sexual offences are presumed to suffer from an individual
pathology that renders them incapable of controlling their behaviour. Treatment
is critical to reduce the probability of recidivism and indeterminate
confinement is the preferred means by which those offenders are incapacitated
until such a time as they are found no longer to be dangerous.

American dangerous offender laws formulated within the clinical framework
make some incorrect assumptions (Petrunik, 1994). For example, violent
offenders are assumed to suffer from some type of mental abnormality that
causes them to re-offend, with their offences getting progressively more
serious. As well, the laws reflect a common misconception that most sex
offenders assault victims who are strangers- in fact, most sexual assaults are
perpetrated by an acquaintance, friend or family member of the victim. The
influence of the clinical model is clearly demonstrated in the presumed ability
to diagnose and treat sex offenders as well as accurately predict
dangerousness. Despite studies in the United States that show dangerousness to
be unpredictable and the fact that dangerousness has never been shown to be an
identifiable personality trait (Mullen & Reinehr, 1982), clinicians still
give predictions regarding individual offenders. This aspect of the clinical
model becomes especially troublesome when a clinical assessment is given in
capital murder trials. In such a situation, Ewing (1983) has found that jurors
who were given a clinical assessment of an offender's dangerousness and
subsequently decided to give a death sentence, had relied heavily upon the
clinical opinion in making their decision.